Failure to Diagnose and Delayed Diagnosis in New York: When a Missed Medical Condition Becomes Negligence

By seriousl January 19, 2026

A missed or late diagnosis can change the course of a person’s health, especially when timely treatment would likely have improved the outcome. In New York, not every diagnostic mistake is malpractice, but some errors cross the line into legally actionable negligence. Understanding the difference can help patients and families recognize when a claim may be appropriate and what information matters most. If you believe a provider missed critical warning signs, a medical malpractice lawyer can help evaluate whether the facts support a claim.

What Is Failure to Diagnose?

Failure to diagnose occurs when a clinician does not identify a medical condition that a reasonably prudent provider would have recognized under similar circumstances. This can involve overlooking “red flag” symptoms, not ordering appropriate tests, misreading diagnostic studies, failing to follow up on abnormal results, or failing to refer a patient to a specialist when the presentation calls for it.

In practice, failure to diagnose often appears in cases involving cancer, infections, heart attack, stroke, internal bleeding, and other time-sensitive conditions where delays can quickly increase the risk of severe injury. The focus is not on whether medicine is imperfect, but whether the diagnostic workup fell below accepted medical practice and harmed the patient.

What Is a Delayed Diagnosis?

A delayed diagnosis means the condition is ultimately identified, but later than it should have been. The legal significance of a delay depends on what the patient lost because of it, such as the chance for earlier treatment, less invasive care, or improved survival. Delay claims often involve progression of disease stage, avoidable complications, extended hospitalization, or permanent impairment that could have been reduced with timely recognition. New York courts regularly analyze these cases through medical proof showing what should have happened sooner and how the delay changed the outcome, including whether earlier intervention would likely have made a meaningful difference.

When Does Failure and Delayed Diagnoses Become Negligence?

In New York, diagnostic mistakes become negligence when a provider departs from accepted medical practice, and that departure is a substantial factor in causing harm. In other words, a poor outcome alone is not enough; the case typically turns on what a reasonably careful provider would have done and whether different care would likely have improved the patient’s outcome. This is why medical records, imaging, lab results, and expert review are central in most claims, particularly when the dispute involves timing, follow-up, and differential diagnosis.

Timing also matters because New York has strict filing deadlines. As a general rule, medical malpractice actions must be started within two years and six months, and in some situations, the time period may be measured from the end of continuous treatment for the same condition. Courts continue to apply and refine the continuous treatment doctrine, including in cases such as Rhodes v Van Valkenburg, where ongoing care is alleged but the later visits do not sufficiently relate to the specific condition that forms the basis of the claim.

New York also has a limited discovery rule for certain cancer misdiagnosis claims, often referred to as Lavern’s Law. For an alleged negligent failure to diagnose cancer or a malignant tumor, a lawsuit may be filed within two years and six months from when the patient knew or reasonably should have known of the failure to diagnose, subject to an outside cap measured from the alleged malpractice. Brennan v MacDonald addressed how these timing rules apply in real cases involving alleged delayed cancer diagnosis and other diagnostic failures.

To evaluate whether a missed or delayed diagnosis rises to malpractice, it is often helpful to ask whether there were clear symptoms or abnormal findings that should have triggered a different response, whether follow-up on test results was reasonable, and whether the delay affected treatment options or prognosis. A medical negligence lawyer reviewing the record will often focus on the critical decision points, such as whether a patient should have been admitted to a hospital, referred for urgent imaging, or treated sooner for an infection or other evolving condition. When the record supports a departure from accepted practice and a provable link to injury, a medical injury lawyer may be able to help a patient pursue compensation for medical costs, lost income, pain and suffering, and, in wrongful death cases, losses recognized under New York law.

Protecting Patients and Families from Missed Diagnosis

Failure to diagnose and delayed diagnosis cases are often decided by details, including what symptoms were documented, what testing was ordered, and what follow-up occurred. New York’s deadlines can be unforgiving, so early review of records is frequently important, especially in cancer cases where the discovery rule may apply.

If you are weighing whether a missed condition became malpractice, contact Poissant, Nichols, Grue, Vanier & Babbie to clarify whether the care likely departed from accepted practice and whether that departure caused measurable harm. Schedule your consultation or call 518-483-1440.